/*
 * aes_icm.c
 *
 * AES Integer Counter Mode
 *
 * David A. McGrew
 * Cisco Systems, Inc.
 */

/*
 *
 * Copyright (c) 2001-2006, Cisco Systems, Inc.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *   Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 *
 *   Redistributions in binary form must reproduce the above
 *   copyright notice, this list of conditions and the following
 *   disclaimer in the documentation and/or other materials provided
 *   with the distribution.
 *
 *   Neither the name of the Cisco Systems, Inc. nor the names of its
 *   contributors may be used to endorse or promote products derived
 *   from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */

#define ALIGN_32 0

#include "aes_icm.h"
#include "alloc.h"
#define LOG_TAG "Srtp-1.4.4"

debug_module_t mod_aes_icm = { 0, /* debugging is off by default */
"aes icm" /* printable module name       */
};

/*
 * integer counter mode works as follows:
 *
 * 16 bits
 * <----->
 * +------+------+------+------+------+------+------+------+
 * |           nonce           |    pakcet index    |  ctr |---+
 * +------+------+------+------+------+------+------+------+   |
 *                                                             |
 * +------+------+------+------+------+------+------+------+   v
 * |                      salt                      |000000|->(+)
 * +------+------+------+------+------+------+------+------+   |
 *                                                             |
 *                                                        +---------+
 *                              | encrypt |
 *                              +---------+
 *                                   |
 * +------+------+------+------+------+------+------+------+   |
 * |                    keystream block                    |<--+
 * +------+------+------+------+------+------+------+------+
 *
 * All fields are big-endian
 *
 * ctr is the block counter, which increments from zero for
 * each packet (16 bits wide)
 *
 * packet index is distinct for each packet (48 bits wide)
 *
 * nonce can be distinct across many uses of the same key, or
 * can be a fixed value per key, or can be per-packet randomness
 * (64 bits)
 *
 */

err_status_t aes_icm_alloc_ismacryp(cipher_t **c, int key_len, int forIsmacryp) {
    extern cipher_type_t aes_icm;
    uint8_t *pointer;
    int tmp;

    debug_print(mod_aes_icm, "allocating cipher with key length %d", key_len);

    /*
     * Ismacryp, for example, uses 16 byte key + 8 byte
     * salt  so this function is called with key_len = 24.
     * The check for key_len = 30 does not apply. Our usage
     * of aes functions with key_len = values other than 30
     * has not broken anything. Don't know what would be the
     * effect of skipping this check for srtp in general.
     */
    if (!forIsmacryp && key_len != 30)
        return err_status_bad_param;

    /* allocate memory a cipher of type aes_icm */
    tmp = (sizeof(aes_icm_ctx_t) + sizeof(cipher_t));
    pointer = (uint8_t*) crypto_alloc(tmp);
    if (pointer == NULL)
        return err_status_alloc_fail;

    /* set pointers */
    *c = (cipher_t *) pointer;
    (*c)->type = &aes_icm;
    (*c)->state = pointer + sizeof(cipher_t);

    /* increment ref_count */
    aes_icm.ref_count++;

    /* set key size        */
    (*c)->key_len = key_len;

    return err_status_ok;
}

err_status_t aes_icm_alloc(cipher_t **c, int key_len, int forIsmacryp) {
    return aes_icm_alloc_ismacryp(c, key_len, 0);
}

err_status_t aes_icm_dealloc(cipher_t *c) {
    extern cipher_type_t aes_icm;

    /* zeroize entire state*/
    octet_string_set_to_zero((uint8_t *) c, sizeof(aes_icm_ctx_t)
            + sizeof(cipher_t));

    /* free memory */
    crypto_free(c);

    /* decrement ref_count */
    aes_icm.ref_count--;

    return err_status_ok;
}

/*
 * aes_icm_context_init(...) initializes the aes_icm_context
 * using the value in key[].
 *
 * the key is the secret key
 *
 * the salt is unpredictable (but not necessarily secret) data which
 * randomizes the starting point in the keystream
 */

err_status_t aes_icm_context_init(aes_icm_ctx_t *c, const uint8_t *key) {
    v128_t tmp_key;

    /* set counter and initial values to 'offset' value */
    /* FIX!!! this assumes the salt is at key + 16, and thus that the */
    /* FIX!!! cipher key length is 16!  Also note this copies past the
     end of the 'key' array by 2 bytes! */
    v128_copy_octet_string(&c->counter, key + 16);
    v128_copy_octet_string(&c->offset, key + 16);

    /* force last two octets of the offset to zero (for srtp compatibility) */
    c->offset.v8[14] = c->offset.v8[15] = 0;
    c->counter.v8[14] = c->counter.v8[15] = 0;

    /* set tmp_key (for alignment) */
    v128_copy_octet_string(&tmp_key, key);

    debug_print(mod_aes_icm, "key:  %s", v128_hex_string(&tmp_key));
    debug_print(mod_aes_icm, "offset: %s", v128_hex_string(&c->offset));

    /* expand key */
    aes_expand_encryption_key(&tmp_key, c->expanded_key);

    /* indicate that the keystream_buffer is empty */
    c->bytes_in_buffer = 0;

    return err_status_ok;
}

/*
 * aes_icm_set_octet(c, i) sets the counter of the context which it is
 * passed so that the next octet of keystream that will be generated
 * is the ith octet
 */

err_status_t aes_icm_set_octet(aes_icm_ctx_t *c, uint64_t octet_num) {

#ifdef NO_64BIT_MATH
    int tail_num = low32(octet_num) & 0x0f;
    /* 64-bit right-shift 4 */
    uint64_t block_num = make64(high32(octet_num) >> 4,
            ((high32(octet_num) & 0x0f)<<(32-4)) |
            (low32(octet_num) >> 4));
#else
    int tail_num = octet_num % 16;
    uint64_t block_num = octet_num / 16;
#endif

    /* set counter value */
    /* FIX - There's no way this is correct */
    c->counter.v64[0] = c->offset.v64[0];
#ifdef NO_64BIT_MATH
    c->counter.v64[0] = make64(high32(c->offset.v64[0]) ^ high32(block_num),
            low32(c->offset.v64[0]) ^ low32(block_num));
#else
    c->counter.v64[0] = c->offset.v64[0] ^ block_num;
#endif

    debug_print(mod_aes_icm, "set_octet: %s", v128_hex_string(&c->counter));

    /* fill keystream buffer, if needed */
    if (tail_num) {
        v128_copy(&c->keystream_buffer, &c->counter);
        aes_encrypt(&c->keystream_buffer, c->expanded_key);
        c->bytes_in_buffer = sizeof(v128_t);

        debug_print(mod_aes_icm, "counter:    %s", v128_hex_string(&c->counter));
        debug_print(mod_aes_icm, "ciphertext: %s", v128_hex_string(
                &c->keystream_buffer));

        /*  indicate number of bytes in keystream_buffer  */
        c->bytes_in_buffer = sizeof(v128_t) - tail_num;

    } else {

        /* indicate that keystream_buffer is empty */
        c->bytes_in_buffer = 0;
    }

    return err_status_ok;
}

/*
 * aes_icm_set_iv(c, iv) sets the counter value to the exor of iv with
 * the offset
 */

err_status_t aes_icm_set_iv(aes_icm_ctx_t *c, void *iv) {
    v128_t *nonce = (v128_t *) iv;

    debug_print(mod_aes_icm, "setting iv: %s", v128_hex_string(nonce));

    v128_xor(&c->counter, &c->offset, nonce);

    debug_print(mod_aes_icm, "set_counter: %s", v128_hex_string(&c->counter));

    /* indicate that the keystream_buffer is empty */
    c->bytes_in_buffer = 0;

    return err_status_ok;
}

/*
 * aes_icm_advance(...) refills the keystream_buffer and
 * advances the block index of the sicm_context forward by one
 *
 * this is an internal, hopefully inlined function
 */

inline void aes_icm_advance_ismacryp(aes_icm_ctx_t *c, uint8_t forIsmacryp) {
    /* fill buffer with new keystream */
    v128_copy(&c->keystream_buffer, &c->counter);
    aes_encrypt(&c->keystream_buffer, c->expanded_key);
    c->bytes_in_buffer = sizeof(v128_t);

    debug_print(mod_aes_icm, "counter:    %s", v128_hex_string(&c->counter));
    debug_print(mod_aes_icm, "ciphertext: %s", v128_hex_string(
            &c->keystream_buffer));

    /* clock counter forward */

    if (forIsmacryp) {
        uint32_t temp;
        //alex's clock counter forward
        temp = ntohl(c->counter.v32[3]);
        c->counter.v32[3] = htonl(++temp);
    } else {
        if (!++(c->counter.v8[15]))
            ++(c->counter.v8[14]);
    }
}

inline void aes_icm_advance(aes_icm_ctx_t *c) {
    aes_icm_advance_ismacryp(c, 0);
}

/*e
 * icm_encrypt deals with the following cases:
 *
 * bytes_to_encr < bytes_in_buffer
 *  - add keystream into data
 *
 * bytes_to_encr > bytes_in_buffer
 *  - add keystream into data until keystream_buffer is depleted
 *  - loop over blocks, filling keystream_buffer and then
 *    adding keystream into data
 *  - fill buffer then add in remaining (< 16) bytes of keystream
 */

err_status_t aes_icm_encrypt_ismacryp(aes_icm_ctx_t *c, unsigned char *buf,
        unsigned int *enc_len, int forIsmacryp) {
    unsigned int bytes_to_encr = *enc_len;
    unsigned int i;
    uint32_t *b;

    /* check that there's enough segment left but not for ismacryp*/
    if (!forIsmacryp && (bytes_to_encr + htons(c->counter.v16[7])) > 0xffff)
        return err_status_terminus;

    debug_print(mod_aes_icm, "block index: %d", htons(c->counter.v16[7]));
    if (bytes_to_encr <= (unsigned int) c->bytes_in_buffer) {

        /* deal with odd case of small bytes_to_encr */
        for (i = (sizeof(v128_t) - c->bytes_in_buffer); i < (sizeof(v128_t)
                - c->bytes_in_buffer + bytes_to_encr); i++) {
            *buf++ ^= c->keystream_buffer.v8[i];
        }

        c->bytes_in_buffer -= bytes_to_encr;

        /* return now to avoid the main loop */
        return err_status_ok;

    } else {

        /* encrypt bytes until the remaining data is 16-byte aligned */
        for (i = (sizeof(v128_t) - c->bytes_in_buffer); i < sizeof(v128_t); i++)
            *buf++ ^= c->keystream_buffer.v8[i];

        bytes_to_encr -= c->bytes_in_buffer;
        c->bytes_in_buffer = 0;

    }

    /* now loop over entire 16-byte blocks of keystream */
    for (i = 0; i < (bytes_to_encr / sizeof(v128_t)); i++) {

        /* fill buffer with new keystream */
        aes_icm_advance_ismacryp(c, forIsmacryp);

        /*
         * add keystream into the data buffer (this would be a lot faster
         * if we could assume 32-bit alignment!)
         */

#if ALIGN_32
        b = (uint32_t *)buf;
        *b++ ^= c->keystream_buffer.v32[0];
        *b++ ^= c->keystream_buffer.v32[1];
        *b++ ^= c->keystream_buffer.v32[2];
        *b++ ^= c->keystream_buffer.v32[3];
        buf = (uint8_t *)b;
#else
        if ((((unsigned long) buf) & 0x03) != 0) {
            *buf++ ^= c->keystream_buffer.v8[0];
            *buf++ ^= c->keystream_buffer.v8[1];
            *buf++ ^= c->keystream_buffer.v8[2];
            *buf++ ^= c->keystream_buffer.v8[3];
            *buf++ ^= c->keystream_buffer.v8[4];
            *buf++ ^= c->keystream_buffer.v8[5];
            *buf++ ^= c->keystream_buffer.v8[6];
            *buf++ ^= c->keystream_buffer.v8[7];
            *buf++ ^= c->keystream_buffer.v8[8];
            *buf++ ^= c->keystream_buffer.v8[9];
            *buf++ ^= c->keystream_buffer.v8[10];
            *buf++ ^= c->keystream_buffer.v8[11];
            *buf++ ^= c->keystream_buffer.v8[12];
            *buf++ ^= c->keystream_buffer.v8[13];
            *buf++ ^= c->keystream_buffer.v8[14];
            *buf++ ^= c->keystream_buffer.v8[15];
        } else {
            b = (uint32_t *) buf;
            *b++ ^= c->keystream_buffer.v32[0];
            *b++ ^= c->keystream_buffer.v32[1];
            *b++ ^= c->keystream_buffer.v32[2];
            *b++ ^= c->keystream_buffer.v32[3];
            buf = (uint8_t *) b;
        }
#endif /* #if ALIGN_32 */

    }

    /* if there is a tail end of the data, process it */
    if ((bytes_to_encr & 0xf) != 0) {

        /* fill buffer with new keystream */
        aes_icm_advance_ismacryp(c, forIsmacryp);

        for (i = 0; i < (bytes_to_encr & 0xf); i++)
            *buf++ ^= c->keystream_buffer.v8[i];

        /* reset the keystream buffer size to right value */
        c->bytes_in_buffer = sizeof(v128_t) - i;
    } else {

        /* no tail, so just reset the keystream buffer size to zero */
        c->bytes_in_buffer = 0;

    }

    return err_status_ok;
}

err_status_t aes_icm_encrypt(aes_icm_ctx_t *c, unsigned char *buf,
        unsigned int *enc_len) {
    return aes_icm_encrypt_ismacryp(c, buf, enc_len, 0);
}

err_status_t aes_icm_output(aes_icm_ctx_t *c, uint8_t *buffer,
        int num_octets_to_output) {
    unsigned int len = num_octets_to_output;

    /* zeroize the buffer */
    octet_string_set_to_zero(buffer, num_octets_to_output);

    /* exor keystream into buffer */
    return aes_icm_encrypt(c, buffer, &len);
}

char aes_icm_description[] = "aes integer counter mode";

uint8_t
        aes_icm_test_case_0_key[30] = { 0x2b, 0x7e, 0x15, 0x16, 0x28, 0xae,
                0xd2, 0xa6, 0xab, 0xf7, 0x15, 0x88, 0x09, 0xcf, 0x4f, 0x3c,
                0xf0, 0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7, 0xf8, 0xf9,
                0xfa, 0xfb, 0xfc, 0xfd };

uint8_t aes_icm_test_case_0_nonce[16] = { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 };

uint8_t aes_icm_test_case_0_plaintext[32] = { 0x00, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, };

uint8_t aes_icm_test_case_0_ciphertext[32] = { 0xe0, 0x3e, 0xad, 0x09, 0x35,
        0xc9, 0x5e, 0x80, 0xe1, 0x66, 0xb1, 0x6d, 0xd9, 0x2b, 0x4e, 0xb4, 0xd2,
        0x35, 0x13, 0x16, 0x2b, 0x02, 0xd0, 0xf7, 0x2a, 0x43, 0xa2, 0xfe, 0x4a,
        0x5f, 0x97, 0xab };

cipher_test_case_t aes_icm_test_case_0 = { 30, /* octets in key            */
aes_icm_test_case_0_key, /* key                      */
aes_icm_test_case_0_nonce, /* packet index             */
32, /* octets in plaintext      */
aes_icm_test_case_0_plaintext, /* plaintext                */
32, /* octets in ciphertext     */
aes_icm_test_case_0_ciphertext, /* ciphertext               */
NULL /* pointer to next testcase */
};

/*
 * note: the encrypt function is identical to the decrypt function
 */

cipher_type_t aes_icm = { (cipher_alloc_func_t) aes_icm_alloc,
        (cipher_dealloc_func_t) aes_icm_dealloc,
        (cipher_init_func_t) aes_icm_context_init,
        (cipher_encrypt_func_t) aes_icm_encrypt,
        (cipher_decrypt_func_t) aes_icm_encrypt,
        (cipher_set_iv_func_t) aes_icm_set_iv, (char *) aes_icm_description,
        (int) 0, /* instance count */
        (cipher_test_case_t *) &aes_icm_test_case_0,
        (debug_module_t *) &mod_aes_icm };

